O'Malley is asked if there is anything he wants to say that he didn't get to say. The question receives laughs from the crowd, particularly since O'Malley has barely been given time to speak. O'Malley mentions immigration, Puerto Rico and conflict in Central America.

Next YouTube question comes from Marques Brownlee for O'Malley on privacy, technology and encryption. O'Malley responds: "The government should get a warrant, whether they want to come in via your back door or front door."

The debate quickly turns to Syria and whether the candidates would put "boots on the ground". Sanders points to the war in Iraq, while O'Malley thanks his fellow candidates for not referring to US servicemen and women as "boots on the ground".

Candidates are asked moving away from fossil fuels and climate change. Sanders calls out Republicans for not believing in climate change, while O'Malley asks his fellow Democratic candidates to join him in pushing for 100% clean energy by 2050.

The debate, nearly an hour in, has been focused on frontrunner Clinton and Sanders. Viewers have noticed that O'Malley has been left largely out of the conversation—including Republican presidential candidate Rand Paul, who's Tweeting the #DemDebate.

Clinton and Sanders spar over Sanders's healthcare propositions. Clinton claims his new plan will destroy Obamacare, adding, "I don't want to see us start over again. I want us to defend and build on the Affordable Care Act and improve it."

We have to move away from treating the use of drugs as a crime and instead, move it to where it belongs, as a health issue. We need to divert more people from the criminal justice system into drug court, into treatment and recovery.